Crane incorporating vertical motion apparatus

ABSTRACT

A crane incorporating vertical movement compensation apparatus. A crane having a boom with suspended hoisting cable is adapted to support a load substantially independent of the vertical movement of the crane and associated apparatus. The hoisting cable is supported by a winch incorporating a continuously slipping clutch which maintains the load in a controlled tension mode. The winch shaft about which is secured the crane drum drives through an overrunning clutch to a braking device to permit the load to be moved in the in-haul direction without interference of the brake while precluding inadvertent downward movement of the load as a result of vertical displacement of the crane.

[ Aug. 26, 1975 3,289,967 12/1966Robinson........................254/173R 1 1 CRANE INCORPORATINGVERTICAL 3,373,972 3/1968 Peterson... 3,500,764 3/1970 Warman 3,651,9053/1972 3,726,801 4/1973 MOTION APPARATUS Brown.........,...

[76] Inventor: Earl A. Peterson, 41 1 l Chestnut Sterner et 192/12 BAve., Long Beach, Calif. 90802 Primary Examiner--Evon C. Blunk AssistantExam iner.leffrey V. Nase 1 7 9 1 m v0b Al 0 N l P MD. FA an 22 RelatedUS. Application Data Continuation-impart of Scr. No. 823,894, May 12,1969, abandoned.

[57] ABSTRACT A crane incorporating vertical movement compensationapparatusJ A crane having a boom with sus- [52] US. 254/139.1; l88/71.2;192/12 13;

pended hoistingcable is adapted to support a load substantiallyindependent of the vertical movement of the crane and associatedapparatus. The hoisting cable is supported by a winch incorporating acontinuously slipping clutch which maintains the load in a con- 12 BAtrolled tension mode. The winch shaft about which is secured the cranedrum drives through an overrunning [561 References C'ted clutch to abraking device to permit the load to be UNlTED STATES PATENTS moved inthe in-haul direction without interference of the brake while precludinginadvertent downward 829,057 8/1906 254/185 R 2.959.396 11/1960 Lawrence254/172 movement of the load as a result of vertical displace- 2,966,221

S e m, m g n i w a f. D 8 s .m e. h m C u 9 e m. f o t n e m BRR 373 7874 M4 5-35 222 mn Mm ed nn .mm KT 046 666 999 HUN 245 PATENTED 3.901 .4!8 I sum 1 [1F 3 I INVENTOR. 222 19. Pe TEE80N PATENTED AUBZBIHYB 3,90 l.47 8

saw 3 OF 3 EARL A. PETERSON INVENTOR SPE/VSLEY, HOE/V8 LUB/ T ZATTORNFYS CRANE INCORPORATING VERTICAL MOTION APPARATUS This applicationis a continuation-in-part of my application Ser. No. 823.894 filed May12, 1969.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention crane apparatus is generally related to the field of hoistingdevices and, in particular, to those devices incorporating apparatus forvertical movement compensation.

2. Prior Art The need to equip marine vessels and other like structureswith winches or cranes which are capable of compensating for thevertical motion of the vessel or supporting structure has long beenrecognized. The ability to vertically lift a load independent of thevertical movement of the crane or winch structure has been a problemwhich has heretofore not been totally resolved by the devices disclosedin the prior art. The requirements for a crane or winch intended forvertically lifting loads are considerably more complicated than systemsdesigned for the horizontal movement of loads. These complications ariseout of the need to institute safeguards to prevent inadvertent releaseof the loads in the event of power failure, vertical movement of thelifting mechanism or other similar occurrances.

One of the devices disclosed by the prior art is set forth in ApplicantsUS. Pat. No. 3,373,972. The device disclosed is a winch incorporating acontinuously slipping clutch to permit movement of loads utilizing thecontrolled tension in the hoisting line of the winch. One of theproblems left unresolved by this device concerns the inability tocompensate for failures in the energy source for the winch or to provideimproved methods for initiating movement of loads without encounteringthe complications inherent in the transition from a static to a dynamiccondition.

Another device disclosed by the prior art constitutes an apparatus forhorizontally transferring loads between displaced stations. Thismechanism in no way encounters the problems of vertically displacedloads since the supporting stations fully provide stability for thehoisting line and the attached loads. The problems sought to be solvedby the present invention are created where loads must be verticallylifted in a manner which will minimize disturbances of the load whileconcurrently eliminating the possibility of dropping the load as aresult of power failures or other adverse conditions.

Another device disclosed by the prior art is used for the drilling ofwell bores, typically in an off-shore environment. The device utilizes afluid coupling in the attempt to compensate for vertical motion of thefloating support structure. A fluid coupling presents inherent problemswith respect to response time, load capacity and control over asupporting load. In addition, the device disclosed by the prior areincludes no means for insuring that the load will not be inadvertentlydropped. In the particular application, a drill string is supported by awinch powered through the fluid coupling. A flaw in this system couldeasily result in damage to the drill string and attached drill bit,problems which are substantially resolved by the present invention.

The present invention crane substantially resolves the problems leftunsolved by the devices disclosed in the prior art. The power source forthe present invention crane is supplied through a continuously slippingclutch coupled to the drum shaft. In order to prevent unintended damageto the load as a result of inadvertent vertical displacement thereof,the drum shaft is coupled to a supplemental braking system through anoverrunning or one-way clutch. In this manner, the load will besupported in an in-haul direction by freewheeling against the brake, theout-haul movement of the hoisting line being subject to a supplementalbraking system.

SUMMARY OF THE INVENTION The present invention comprises a crane havingmeans for compensating for vertical displacement of the crane supportingstructure as well as incorporated apparatus for preventing inadvertentout-haul movement of the hoisting line. The present invention craneincorporates a boom supported by an adjustable block and tackle assemblyor other like structure. The hoisting line is supported by a sheave atthe top of the boom, the hoisting line being wound about and secured tothe hoisting drum. The drum is securely mounted upon the drum shaft, theshaft being powered through a continuously slipping clutch. The housingof the clutch is driven in an over-speeded condition to insure thatthere is a predetermined speed differential between the driving anddriven elements of the clutch. A tension measuring device is responsiveto the tension in the hoisting line, the tension measuring deviceproviding an output indicative of any adjustment to be made to therespect to the output torque of the continuously slipping clutch. Thetension measuring device is coupled to the continuously slipping clutchto enable incremental changes in the output torque of the continuouslyslipping clutch to maintain a controlled tension in the hoisting line.

The driving element of the continuously slipping clutch rotates in thein-haul direction, the speed differential between the driving and drivenelements of the clutch insuring adequate recovery rates for verticaldisplacement of the crane assembly. To prevent inadvertent verticaldisplacement of the load supported on the hoisting line, the drum shaftis run through a one-way clutch to a supplemental braking system. Whenthe braking system is actuated, the drum clutch will rotate in thein-haul direction in a free-wheeling mode independent of the brakingsystem, any out-haul movement of the clutch being subject to the actionof the braking system. The present invention crane permits upward ordownward movement of the load by the operation of the clutch in acontinuously slipping mode, the movement being controlled by controlover the output torque of the clutch. By driving the drum shaft througha one-way or overrunning clutch and allowing same to rotate in thein-haul direction in a free-wheeling manner, a load can be supported bythe braking system yet in-haul movement initiated totally free of anyinadvertent and adverse vertical displacement of the load.

It is therefore an object of the present invnetion to provide a craneincorporating vertical movement compensating apparatus.

It is another object of the present invention to provide an improvedcrane apparatus to prevent inadvertent vertical displacement of asupported load.

It is still another object of the present invention to A provide a cranecapable of compensating for vertical displacement of the crane as wellas apparatus for eliminating the adverse affect resulting from thetransition from static to dynamic movement of the load.

It is still yet another object of the present invention to provide acrane for initiating upward vertical displacement of a load from astatic condition substan tially eliminating perturbations of the load.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objectives and advantages thereof, will be betterunderstood from the following description considered in connection withthe accompanying drawing in which a presently preferred embodiment ofthe invention is illustrated by way'of example. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only and is not intended as a definition of the limitsof the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. is a side elevation, partialcross-sectional view of the one-way clutch of FIG. 4 taken through line55 of FIG. 4.

FIGS. 6a, 6b and 6c are schematic, partial crosssectional views of aone-way clutch illustrating the mode of operation thereof.

DESCRIPTION OF THE PRESENTLY PREFERIRED EMBODIMENT I An understanding ofthe structure of the present invention'apparatus can be best gained byreference to FIG. '1 wherein a perspective view of acrane' incorporatingthe elements of the invention is shown therein, the crane beinggenerally designated by the reference numeral 1'. Crane l is constructedupon platform 2, platform 2 being a portion of a floating or fixedstructure. As stated, an object of the present invention is to provide'a crane capable of vertical motion compensation as is typicallyencountered in off-shore applications. Although a preferred embodimentof the present invention is utilized upon a marine vessel or otherfloating support structure, the scope of the present inventionencompasses the same with fixed structures. A hoisting assembly 3 iscoupled to boom 4 for the purpose of orienting boom 4 in any desiredposition. Load 5 is supported by hoisting cable 6. To raise and lowerboom 4, cable 7 is secured to the upper portion thereof, cable 7 beingcoupled to hoisting assembly 3 by block and tackle assembly 8. Althoughthe scope of the present invention embodies the use of same with agantry, A-frame derrick or similar structure, the preferred embodimentof the present invention utilizes the boom assembly as shown in FIG. 1.I

Hoisting cable 6 is disposed over sheave I0, portion 9 of hoisting cable6 being disposed for measurement of the tension therein as will beexplained in detail be;

low. Hoisting cable 6 is supported and disposed around drum' 11, thewinch assembly coupled thereto being powered by motor 12. Motor 12 iscoupled to clutch 14, clutch 14 being coupled to shaft 15 which supportsdrum 11 and is coupled to brake assembly 13 as will be explained indetail below. The operation of motor 12, clutch 14, drum 11 andassociated hoisting cable 6 are similar to that described in ApplicantsUS. Pat. No. 3,373,972.

The ability of the present invention to maintain constant tension inhoisting cable 6 irrespective of vertical displacement of platform 2 canbe best understood byreference to FIG. 2 wherein a side elevation,crosssectional view of clutch 14 is shown. Clutch 14 is one capable ofone operating in a continuously slipping mode whereby a predeterminedspeed differential can be maintained between the driving anddriven'elements of clutch 14. Motor 12 is coupled to drive ring- 16which is concentrically disposed about and journeled upon shaft 15 bysuitable bearings 17. Drive ring '16 is securely coupled'to clutchhousing 18. The preferred embodimentof the present invention utilizes amotor 12 having a substantially constant output torque which is imposedupon clutch housing 18 through drive ring 16. The driving elements ofclutch 14 which are concentrically disposed within and adapted to rotatewith housing 18 are friction elements 19 and 20. Friction elements 19and 20 are disposed at axially opposed interior surfaces of housing 18,friction element 20 being axially moveable upon the introduction ofactuating energy at expandable element 21. Driven friction disc 22- isconcentrically disposed about and secured to clutch hub 23 by splineteeth or other suitable coupling means. Clutch 14 is suitable to allow apredetermined differential speed to be maintained between drivingfriction elements 19 and 20 and driven friction disc 22. In order todissipate the heat horsepower generated at friction discs 19 and 20,annular channels 24 are-disposed in clutch housing 18 adjacent frictionelements 19 and 20 to appropriately dissipate the generated heat.Annular channels 24 and 25 are adapted to receive appropriate coolingliquid such as water. In order to,.pr ovide for cooling of clutch 14through the use of liquid-coolant, roto-coupling 26 provides for coolantinput and output lines 27 and 28, the connections between the coolantlines and annular channels 24 and 25 not shown.

As stated, friction elements 19 and 20 will frictionally engage frictiondisc 22 upon actuation of expandable element 21. Expandable element 21is typically an air actuated element. Air is introduced at rote-coupling29, the air line being designated by the. reference numeral 30. Air isdistributed at ring 31, the output line 32 being coupled to input line33 of expandable elements 21. Thecoupling between output line 32 andinput coupling 33 not being shown.

As stated, the output of motor 12 provides the driving torque on clutchhousing 18 which is transmitted to friction disc 22 through frictionelements 19 and 20. The output torque of clutch 14 appears at shaft 15and is determined by the level of actuationat expandable element2l.Drive ring 16 and therefore clutch housing 18 constantly rotates in thein-haul direction, the output torque on shaft 15 being controlledtomaintain a predetermined tension in hoistingcable 6 (FIG. 1). Bymaintaining a speed differential between clutch housing 18 and shaft 15,the tension in hoistingcable 6 will maintain-load 5 in a dynamiccondition whereby load 5 can be raised or lowered by adjusting the airpressure at expandable element 21. in "addition, maintaining cable 6 ina controlled tension mode will permit accurate control over thein-haul/out-haul or stationary mode of hoisting cable 6 and load 5.Although it is within the scope of the present invention to implementclutch 14 by a number of conventional clutches, clutch 14 is preferablyan air actuated, water cooled disc clutch capable of operating in acontinuously slipping mode wherein there is a controlled differentialspeed between clutch hub 23 and housing 18 and therefore betweenfriction disc 22 and friction elements 19 and 20.

An understanding of the apparatus used to control the tension inhoisting cable 6 can be best seen by reference to FIG. 3 wherein aschematic diagram of the regulating system, clutch 14, braking system 13and a tension measuring device can be best seen, the regulating systembeing generally designated by the reference numeral 60. Load cell ortensiometer 61 is coupled to portion 9 of hoisting cable 6, load cell 61being a conventional device adapted for sensing and measuring thetension line. Load cell 61 is responsive to the tension in hoistingcable 6, changing the hydraulic pressure in pressure line 34 inproportion to the tension in hoisting cable 6. Gauge 35 is coupled topressure line 34 to visually illustrate the tension in hoisting cable 6.

As stated, the output of load cell 61 is coupled to regulator 60 bypressure line 34. One of the advantages of the present invention is toprovide simplified control over operation of the present invention cranestructure. As shown in FIG. 3, a single manual control 62 will permitfull control over the operation of the tension regulating system as wellas braking assembly 13. Air under pressure is input at pressure line 36from a conventional pressure source not shown. Pressure line 36 conductsthe pressurized air to the variable air pressure load control valve 37and variable brake release valve 38. The variable air pressure valve 37is actuated by manual control 62 as shown, the output of valve 37 beingconnected to the conventional selector valve 39. Pressure line 40couples the output of variable brake release valve 38 to the spring setair release of braking assembly 13.

Regulator 60 includes bellows chamber 41 which is coupled to hydraulicpneumatic transducer 42 by pressure line 43. Although it was stated thatload cell 61 produces a hydraulic or pneumatic pressure output, it isobvious that load cell 61 could be fabricated from any sensing devicewhich is compatible with the selected transducer 42. The output oftransducer 42 is coupled to regulator valve 44 through pressure line 45.Air is introduced to regulator valve 44 from pressure line 36 viapressure line 46. A conventional booster relay 47 is serially coupled inpressure line 36 and therefore to air line 30 of rote-coupling 29 viapressure line 48. Bellows chamber 49 receives pressurized air from resetrate adjustment valve 50, valve 50 receiving pressurized air fromproportional valve 51 via pressure line 52. Proportional valve 51 iscoupled to relay valve 53 by pressure line 54. Pressurized air is sup,lied to relay valve 53 and proportional valve 51 through pressure line55 which extends from selector valve 39. As a result of theabove-defined coupling, the elements of regulator 60 are pressurized andcontrollable from manual control 62.

In operation, when the output of load cell 61 increases the pressure inpressure line 34, this in turn will increase the pressure in bellowschamber 41 via the output transducer 42 and coupling pressure line 43.The increase in pressure in bellows chamber 41 will move plate 56upwardly toward nozzle 57 to simultaneously increase the pressure atbooster relay 47 and proportional valve 51 and therefore at the input tobe]- lows chamber49. The increase in pressure at bellows chamber 49 willhalt the increase in pressure to booster relay 47. The pressure in thepressure line leading to bellows chamber 49 will slowly pass throughreset rate adjustment valve and will increase the pressure in the lowerpart of bellows chamber 49. This will cause plate 56 to move towardsnozzle 57, again increasing the pressure throughout the system tobooster relay 47 and the upper part of bellows 49. This build up inpressure will increase pressure through the reset rate adjustment valve50 to the lower part of bellows chamber 49 and start another increasethroughout the system and to booster relay 47. The increase in pressurein the system will continue until the pressure from load cell 61 andtransducer 42 is decreased and the system is brought back to itspredetermined set point as established at control valve 63.

The adjustment of the output torque of clutch 14 via regulator 60 willincrease or decrease the output torque based upon the tension inhoisting cable 6. Where it is desired to maintain the stability of load5 irrespective of the verticaldisplacement of platform 2, drum l1 andthe coupled hoisting cable 6 will adapt to the changing verticaldisplacement of platform 2. As discussed, a predetermined differentialspeed is maintained between clutch housing 18 and coupled frictionelements 19 and 20, and the driven friction disc 22 and coupled shaft15. The differential speed between the pair of members will change tomaintain controlled tension in hoisting cable 6. Where platform 2 ismoving vertically downward, the tension in hoisting cable 6 will tend toincrease and therefore drum l1 and hoisting cable 6 will move in theout-haul direction to compensate for the vertical displacement. Whenplatform 2 is moving vertically upwardythe tension in cable 6 would tendto decrease, drum 11 and hoising cable 6 being moved in the in-hauldirection to compensate for this vertical displacement. The combinationof load cell 61 and coupled regulator 60 maintains the tension inhoisting cable 6 at the preset level established at valve 63. Whenhoisting cable 6 and attached load 5 are to be vertically moved,operation of manual control 62 enables movement of hoisting cable 6 inthe desired direction while maintaining proper compensation for verticaldisplacement of platform 2 and the crane elements.

As stated, an object of the present invention was to provide means forinitiating the movement of load 5 when same was being held by brakingassembly 13. In order to accomplish this, the present invention crane 6provides the ability to initiate upward vertical displacement of load 5negating the effect of braking assembly 13 while imposing the effects ofbraking assembly 13 to prevent inadvertent downward displacement of load5. Referring now to FIG, 4, an understanding of the structure used toimplement the safeguard apparatus can be best seen. Drum 11 is keyed toshaft 15, hoisting cable 6 being disposed thereon. Shaft 15 is extendedto and coupled within overrunning or one-Way clutch 70. The outer raceof overrunning clutch is coupled to shaft 71 which is in axial alignmentwith shaft 15. Shaft 71 is coupled to and secured within hub 72 of brakeassembly l3. Overrunning clutch 70 will be explained in detail below.Although the scope of the present invention is broad enough to permitbrake assembly 13 to be fabricated by any number of conventional brakingsys' terns such as air actuated band brakes, brake assembly 13 ispreferably an air actuated disc brake. Brake assembly 13 comprises outerhousing 73 which is rotatably mounted about shaft 71 on suitablebearings 74. Friction elements 75 and 78 are concentrically disposedwithin brake housing 73 and can be caused to frictionally engagefriction disc 76 upon the actuation of expandable elements 77 throughrote-coupling 79. The coupling, roto-coupling 79 and expandable elementsare not shown. Brake housing 73 is referenced to a fixed frame ofreference such as platform 2. Friction disc 76 is concentricallydisposed upon and secured to clutch hub 72 which in turn is keyed toshaft 71. The actuation of brake assembly 13 will cause the relativemotion between shaft 71 and brake housing 73 to cease.

An understanding of overrunning clutch 70 can be best gained byreference to FIG. 5. FIG. is a schematic, partial cross-sectional viewof a cam-clutch utilized to implement overrunning clutch 70. It shall beunderstood that the terms cam-clutch, overrunning clutch or one-wayclutch are synonomous with respect to the use within the presentinvention. Axially disposed on opposite ends of overrunning clutch 70are cylindrical bores 80 and 81 for receiving shafts 71 andrespectively. Keys 82 and 83 are axially aligned with cylindrical bores80 and 81 respectively and will prevent inadvertent rotation of shaft 71or 15 with respect to overrunning clutch 70. Shaft 71 is secured toouter race 84 and drum shaft 15 is secured to inner race 85. Inner race85 is rotatably disposed within outer race 84, inner race 85 beingsuitably journeled within outer race 84 by bearings 86. Carns 87frictionally engage the inner cylindrical surface of outer race 84 andthe outer cylindrical surface of inner race 85. The orientation of cams87 is controlled by outer cage 88 and inner cage 89.

The operation of overrunning clutch 70 can be best seen by reference toFIG. 6a, FIG. 6b and FIG. 6c wherein schematic views of the operation ofoverrunning clutch 70 are shown. As stated, overrunning clutch 70 isused to allow drum shaft 15 to free-wheel with respect to shaft 71 whenbraking assembly 13 is engaged and it is desired to initiate movement ofload 5 and hoisting cable'6 in the in-haul direction. Overrunning clutch70 will effectively lock drum shaft 15 and shaft 71 when drum 11 ispaying out hoisting cable 6 in the out-haul direction. When brakingassembly 13 is engaged, hoisting cable 6 can be payed out only againstthe force of brake assembly 13.

Referring now to FIG. 6a, the free-wheeling mode of overrunning clutch70 is illustrated therein. Inner race 85 and outer race 84 will befree-wheeling with respect to each other when the respective angularrotation is as shown. Inner race 85 is being rotated in acounterclockwise manner whereby hoisting cable 6 is being reeled in upondrum 11 through the action of clutch 14.

Inner cage 89 and outer cage 88 are concentric with re- 6 spect to eachother, each transverse edge of each section of inner cage 89 and outercage 88 contacting a point on cam 87. In this mode, inner cage 89rotates counterclockwise with respect to outer cage 88 orienting cams 87to allow inner race 85 to be in an overrunning condition with respect toouter race 84. Since the top and bottom surfaces of cams 87 are notforced against the respective radial surfaces of inner and outer races85 and 84, the shafts coupled to inner and outer races 85 and 84 will beeffectively disengaged from each other thereby precluding thetransmission of torque from one shaft to the other. Springs 90 insurethat cams 87 maintain contact with races 84 and 85.

Referring now to FIG. 6b, a mode of operation is illustrated wherebyouter race 84 is rotated counterclockwise with respect to inner race 85thereby effectively engaging overrunning clutch and providing for thetransmission of torque from shaft 71 to shaft 15. It will be recognizedthat this mode of operation is not encountered since brake assembly 13does not initiate any rotational force. This mode would be utilizedwhere brake assembly 13 was replaced by a clutch and power source usedto counter the over-haul movement of dwm 11 and attached hoisting cable6. As can be seen by comparing FIG. 6b with FIG. 6a, outer cage 88 andinner cage 89 have rotated counterclockwise with respect to each otherforcing cams 87 to rotate counterclockwise thereby loading overrunningclutch 70 and effectively locking shaft 71 and drum shaft 15. Theloading of overrunning clutch 70 will provide for the transmission oftorque from shaft 71 to drum shaft 15.

Referring now to FIG. 6c, overrunning clutch 70 is illustrated under themode whereby inner race is rotated clockwise with respect to outer race84, this mode arising where hoisting cable 6 is being payed out andbrake assembly 13 engaged. In this configuration, inner cage 89 will berotated clockwise with respect to outer cage 84 thereby fully loadingearns 87 and imposing the force of brake assembly 13 on the outhaulmovement of drum 11. Where there is effective engagement between drumshaft 15 and shaft 71, brake assembly 13 will act as a braking systemthereby providing for the safeguard needed to initiate upward verticaldisplacement of load 5 while load 5 is being held by braking assembly 13as well as preventing inadvertent downward vertical displacement of load5.

The present invention crane provides means for compensating for verticaldisplacement of the supporting platform as well as providing means fordynamically initiating the vertical movement of a load without thesevere problems inherent in systems disclosed by the prior art. Theability to initiate the upward vertical movement of a suspended loadwithout encountering deleterious perturbations yields a system whichprovides substantial advantages regarding economy, safety and ease ofoperation.

I claim:

1. A crane apparatus for use with a supported platform comprising:

a. a boom pivotally secured to the platform;

b. a first shaft;

c. a drum concentrically disposed about and secured to said first shaft;

d. a hoisting cable secured to said drum and moveably disposed over saidboom;

e. a continuously slipping clutch having an outer housing and inner hubcoupled to frictionally r0- tate with respect to each other and fluidmeans for dissipating the frictionally generated heat therein, saidinner hubbeing securely coupled to said first shaft whereby saidhoisting cable is maintained in;

a controlled tension mode;

f. a second shaft;

g. an overrunning clutch interposed between said first and second shaftshaving means. for.engaging said first and second shafts when said drumis pay ing out hoisting cable whereby said overrunning clutch is in afree-wheeling mode when said drum is rotating to reel in hoisting cable;and

h. a brake interposed between said second shaft and the platform wherebybraking force is imposed on the hoisting cable when said drum isrotating to pay out hoisting cable.

2. A crane apparatus as defined in claim 1 wherein said continuouslyslipping clutch includes a friction disc secured to said inner hub,friction elements adapted to slidably engage and rotate with said outerhousing, said fluid means for dissipating heat adjacent said frictionelements, and air actuated expandable elements secured to said housingand adjacent said friction elements, whereby said friction elementsfrictionally engage said friction disc upon actuating said expandableelements.

3. A crane apparatus as defined in claim 2 including tension measuringmeans for measuring the tension in said hoisting cable and outputtingindicia of same, said tension measuring means including tensiontransducing means for detecting the tension in said hoisting cable andoutputting indicia of same, and pressure means for outputting apressurized source responsive to the output of said tension transducingmeans, said tension transducing means being coupled to said hoistingcable, said pressure means being coupled intermediate said tensiontransudcing means and said expandable elements.

4. A crane apparatus as defined in claim 1 including a constant speedpower source coupled to the housing of said continuously slipping clutchwhereby said housing is rotated at a constant speed.

5. A crane apparatus for use with a supported platform comprising:

a. a boom pivotally secured to the platform;

b. a drum shaft;

c. a drum concentrically disposed upon and secured to drum shaft;

d. a hoisting cable disposed about said drum, a portion thereofsuspended over said boom whereby a load is supported;

e. a constant speed power source;

f. a continuously slipping clutch having an inner hub and outer housing,a friction disc secured to said inner hub, friction elements adapted toslidably engage and rotate with said outer housing, fluid means fordissipating heat adjacent said friction el ements. and air actuating,expandable elements secured to said housing and adjacent said frictionelements whereby said friction elements frictionally engage saidfriction disc upon actuating said expandable elements maintaining aspeed differential therebetween, said inner hub being concentricallydisposed upon and secured to said drum shaft, said continuously slippingclutch keeping said hoisting cable in a controlled tension mode;

g. a brake shaft spaced from and in ax'al alignment with said drumshaft;

h. an overrunning clutch interposed between and secured to said drumshaft and said brake shaft, said kit overrunning clutch adapted tofree-wheel said drum shaft with respect to said brake shaft and couplesaid shafts upon alternate rotational move ment of said drum shaftwhereby said shafts rotate together whensaid drum is rotating to pay outsaid hoisting" cable; i I i i. tension measuring means for measuring thetension in said hoisting cable and producing a hydraulic pressuresignalporportional to the tension in said hoisting cable, said tensionmeans including a tension transducer and pressure output means forproducing said hydraulic pressure signal, said tension transducer beingin cooperative relationship with said hoisting cable and producing anoutput signal responsive to the tension in said hoisting cable, saidpressure output means being coupled intermediate to said tensiontransducer and said expandable elements; and j. a brake interposedbetween said brake shaft and the platform whereby braking force isimposed on said hoisting cable when said drum is rotating to pay out thehoisting cable.

6. In combination with a platform mounted crane including a pivotal boomand a power source for the poistioning of the boom, a vertical motioncompensating apparatus comprising:

a. a drum shaft;

b. a drum concentrically disposed about and secured to said drum shaft;

c. a hoisting cable disposed about said drum, a portion thereofsuspended over the boom whereby a load is supported;

d. a continuously slipping clutch having an inner hub and outer housing,and having a friction disc secured to said inner hub, friction elementsadapted to slidably engage and rotate with said outer housing, fluidmeans for dissipating heat adjacent said friction elements, and airactuated, expandable elements secured to said housing and adjacent saidfriction elements, said inner hub being disposed about and secured tosaid drum shaft whereby a speed differential is maintained between saidfriction elements and said friction disc keeping said hoisting cable ina controlled tension mode;

e. a brake shaft, in spaced relation with and in axially alignment withsaid drum shaft;

f. an overrunning clutch interposed between and coupled to said drumshaft and said brake shaft, said overrunning clutch adapted tofree-wheel said drum shaft with respect to said brake shaft and couplesaid shafts upon alternate rotational movement of said drum shaftwhereby said shafts rotate together when said drum is rotating to payout the hoisting cable; and

g. a brake interposed between said brake shaft and the platform wherebybraking force is imposed on said hoisting cable when said drum isrotating to pay out the hoisting cable.

7. A vertical motion compensating apparatus as defined in claim 6including tension measuring means for measuring the tension in saidhoisting cable and outputting indicia of same, said tension measuringmeans including tension transducing means for detecting the tension insaid hoisting cable and outputting indicia of same, and pressure meansfor outputting a pressurized source responsive to the output of saidtension transducing means, said tension transducing means being hoistingcable.

9. 'A vertical motion compensating apparatus as defined in claim 6including a constant speed power source coupled to the housing of saidcontinuously slipping clutch whereby said housing rotates at a constantspeed.

1. A crane apparatus for use with a supported platform comprising: a. aboom pivotally secured to the platform; b. a first shaft; c. a drumconcentrically disposed about and secured to said first shaft; d. ahoisting cable secured to said drum and moveably disposed over saidboom; e. a continuously slipping clutch having an outer housing andinner hub coupled to frictionally rotate with respect to each other andfluid means for dissipating the frictionally generated heat therein,said inner hub being securely coupled to said first shaft whereby saidhoisting cable is maintained in a controlled tension mode; f. a secondshaft; g. an overrunning clutch interposed between said first and secondshafts having means for engaging said first and second shafts when saiddrum is paying out hoisting cable whereby said overrunning clutch is ina free-wheeling mode when said drum is rotating to reel in hoistingcable; and h. a brake interposed between said second shaft and theplatform whereby braking force is imposed on the hoisting cable whensaid drum is rotating to pay out hoisting cable.
 2. A crane apparatus asdefined in claim 1 wherein said continuously slipping clutch includes afriction disc secured to said inner hub, friction elements adapted toslidably engage and rotate with said outer housing, said fluid means fordissipating heat adjacent said friction elements, and air actuatedexpandable elements secured to said housing and adjacent said frictionelements, whereby said friction elements frictionally engage saidfriction disc upon actuating said expandable elements.
 3. A craneapparatus as defined in claim 2 including tension measuring means formeasuring the tension in said hoisting cable and outputting indicia ofsame, said tension measuring means including tension transducing meansfor detecting the tension in said hoisting cable and outputting indiciaof same, and pressure means for outputting a pressurized sourceresponsive to the output of said tension transducing means, said tensiontransducing means being coupled to said hoisting cable, said pressuremeans being coupled intermediate said tension transudcing means and saidexpandable elements.
 4. A crane apparatus as defined in claim 1including a constant speed power source coupled to the housing of saidcontinuously slipping clutch whereby said housing is rotated at aconstant speed.
 5. A crane apparatus for use with a supported platformcomprising: a. a boom pivotally secured to the platform; b. a drumshaft; c. a drum concentrically disposed upon and secured to drum shaft;d. a hoisting cable disposed about said drum, a portion thereofsuspended over said boom whereby a load is supported; e. a constantspeed power source; f. a continuously slipping clutch having an innerhub and outer housing, a friction disc secured to said inner hub,friction elements adapted to slidably engage and rotate with said outerhousing, fluid means for dissipating heat adjacent said frictionelements, and air actuating, expandable elements secured to said housingand adjacent said friction elements whereby said friction elementsfrictionally engage said friction disc upon actuating said expandableelements maintaining a speed differential therebetween, said inner hubbeing concentrically disposed upon and secured to said drum shaft, saidcontinuously slipping clutch keeping said hoisting cable in a controlledtension mode; g. a brake shaft spaced from and in axial alignment withsaid drum shaft; h. An overrunning clutch interposed between and securedto said drum shaft and said brake shaft, said overrunning clutch adaptedto free-wheel said drum shaft with respect to said brake shaft andcouple said shafts upon alternate rotational movement of said drum shaftwhereby said shafts rotate together when said drum is rotating to payout said hoisting cable; i. tension measuring means for measuring thetension in said hoisting cable and producing a hydraulic pressure signalporportional to the tension in said hoisting cable, said tension meansincluding a tension transducer and pressure output means for producingsaid hydraulic pressure signal, said tension transducer being incooperative relationship with said hoisting cable and producing anoutput signal responsive to the tension in said hoisting cable, saidpressure output means being coupled intermediate to said tensiontransducer and said expandable elements; and j. a brake interposedbetween said brake shaft and the platform whereby braking force isimposed on said hoisting cable when said drum is rotating to pay out thehoisting cable.
 6. In combination with a platform mounted craneincluding a pivotal boom and a power source for the poistioning of theboom, a vertical motion compensating apparatus comprising: a. a drumshaft; b. a drum concentrically disposed about and secured to said drumshaft; c. a hoisting cable disposed about said drum, a portion thereofsuspended over the boom whereby a load is supported; d. a continuouslyslipping clutch having an inner hub and outer housing, and having afriction disc secured to said inner hub, friction elements adapted toslidably engage and rotate with said outer housing, fluid means fordissipating heat adjacent said friction elements, and air actuated,expandable elements secured to said housing and adjacent said frictionelements, said inner hub being disposed about and secured to said drumshaft whereby a speed differential is maintained between said frictionelements and said friction disc keeping said hoisting cable in acontrolled tension mode; e. a brake shaft, in spaced relation with andin axially alignment with said drum shaft; f. an overrunning clutchinterposed between and coupled to said drum shaft and said brake shaft,said overrunning clutch adapted to free-wheel said drum shaft withrespect to said brake shaft and couple said shafts upon alternaterotational movement of said drum shaft whereby said shafts rotatetogether when said drum is rotating to pay out the hoisting cable; andg. a brake interposed between said brake shaft and the platform wherebybraking force is imposed on said hoisting cable when said drum isrotating to pay out the hoisting cable.
 7. A vertical motioncompensating apparatus as defined in claim 6 including tension measuringmeans for measuring the tension in said hoisting cable and outputtingindicia of same, said tension measuring means including tensiontransducing means for detecting the tension in said hoisting cable andoutputting indicia of same, and pressure means for outputting apressurized source responsive to the output of said tension transducingmeans, said tension transducing means being coupled to said hoistingcable, said pressure means being coupled intermediate said tensiontransducing means and the expandable elements of said continuouslyslippint clutch.
 8. A vertical motion compensating apparatus as definedin claim 7 wherein said pressurized source is hydraulic pressureproportional to the tension in said hoisting cable.
 9. A vertical motioncompensating apparatus as defined in claim 6 including a constant speedpower source coupled to the housing of said continuously slipping clutchwhereby said housing rotates at a constant speed.